[Blackwheel]

Is one preferable over the other when it comes to the input on your amp? Any difference in sound quality?

 

[earthpeople]

For a portable headphone amp, 3.5mm is likely preferred since it is smaller, allowing for a smaller amp overall (probably).

 

[krmathis]

I prefer 3.5mm input on portable amplifiers, since size is a factor.
Sound wise there should be no or minimal difference.